No abstract

The effect of relative humidity (RH) and temperature on the survival of airborne bovine rotavirus UK isolate (BRV-UK) and a murine rotavirus (MRV) was studied. In any one experiment, the virus under test was suspended in tryptose phosphate broth (TPB) supplemented with uranine (physical tracer) and an antifoam, was aerosolized using a Collison nebulizer into the rotating drum with the RH at either low (30 +/- 5%), medium (50 + 5%) or high (80 +/- 5%) level at 20 +/- 1 degrees C. Following a 15-min period of viral aerosol stabilization, sequential samples of drum air were collected using an All-Glass Impinger (AGI) for 24 h post-aerosolization. Both of the rotavirus isolates were found to survive best at medium RH level and high RH was found least favorable for the survival of these aerosolized rotaviruses. The survival pattern of aerosolized MRV was found to be the best when compared with survival pattern of all animal and human rotavirus isolates studies performed under aerosolized conditions in our laboratory. The findings of these experiments confirm and extend our previous reports on the survival of other animal and human aerosolized rotaviruses and emphasize the fact that air may be one of the vehicles for their dissemination and could explain why it is difficult to control nosocomial outbreaks of rotavirus gastroenteritis and to keep animal colonies rotavirus-free.

At any stage of growth of a wild-type bakers' yeast, some 20% of the catalatic activity of crude extracts is not precipitable by means of antibody prepared against the typical catalase (catalase T), whose purification and properties have been previously described. Some of this catalatic activity is due to the presence of an atypical catalase (catalase A), a heme protein, with a molecular weight estimated as 170 000 – 190 000, considerably lower than that of the usual catalases (225 000 – 250 000). Preparations of catalase A were found to be homogeneous in the analytical ultracentrifuge and in polyacrylamide gel electrophoresis. Its subunit molecular weight, determined from its iron content, was 46 500, virtually the same as that of the major band obtained in gel electrophoresis in the presence of sodium dodecyl sulfate, suggesting that the native protein is tetrameric. Its specific activity is in the range of those reported for other typical catalases.

A method has been devised for directly detecting and monitoring genetically engineered microorganisms (GEMs) by using in vitro amplification of the target DNAs by a polymerase chain reaction and then hybridizing the DNAs with a specific oligonucleotide or DNA probe. A cloned 0.3-kilobase napier grass (Pennisetum purpureum) genomic DNA that did not hybridize to DNAs isolated from various microorganisms, soil sediments, and aquatic environments was inserted into a derivative of a 2,4-dichlorophenoxyacetic aciddegradative plasmid, pRC10, and transferred into Escherichia coli. This genetically altered microorganism, seeded into filter-sterilized lake and sewage water samples (104/ml), was detected by a plate count method in decreasing numbers for 6 and 10 days of sample incubation, respectively. The new method detected the amplified unique marker (0.3-kilobase DNA) of the GEM even after 10 to 14 days of incubation. This method is highly sensitive (it requires only picogram amounts of DNA) and has an advantage over the plate count technique, which can detect only culturable microorganisms. The method may be useful for monitoring GEMs in complex environments, where discrimination between GEMs and indigenous microorganisms is either difficult or requires time-consuming tests.

The ability of clinical and carrier isolates of Neisseria meningitidis to adhere to human buccal epithelial cells and erythrocytes was investigated. Four of the 10 fimbriated strains were able to hemagglutinate. Serial subculture of three of these strains resulted in a loss of ability to hemagglutinate and was coincident with a loss offimbriation. Other fimbriated strains were unable to hemagglutinate but did adhere to buccal epithelial cells. Subculture of one of these strains for as many as 42 passages did not result in loss of fimbriation or ability to adhere to buccal epithelial cells. The attachment of this strain to buccal epithelial cells was inhibited by glycoconjugates. Further, pH exerted different influences on the attachment of hemagglutinating and non-hemagglutinating fimbriated strains to buccal epithelial cells and erythrocytes. The results suggest that different fimbrial mechanisms are involved in the attachment of N. meningitidis to different cell types and that hemagglutination is not an absolute test for fimbriae.